Grinding vs turning

[SamJimenez]

Hello all,

I am trying to compare the merits of grinding vs turning for a particular application but have not had much success on the Internet, so am turning to you guys for some advice.

I am looking to remove between 100 and 400 micro m from a cast iron workpiece in a single operation. The piece will be fed over the grinder at between 10 and 30 mm/min. The required surface finish is 2 micro m RA or better.
Turning is an option, but the requirements are on the limit of what turning processes usually deal with, hence the questions:

Is grinding feasible in this case? If so, can you suggest a particular type or configuration? What problems could this operation encounter?

Many thanks in advance

 

[Compositepro]

2 microns is a mirror finish. I don't think you can get that in one step and at those feed rates.

 

[SamJimenez]

Thanks for your answer.

If this operation was performed in 2 passes I would hope to remove 100-400 micro m in the first and then just enough to achieve the mirror finish in the second. In this case, what sort of feed rates should I be considering? Could I go as far as 100?

Thanks for your time

 

[DennisP]

2.0 Ra is far from a mirror finish. The only means to remove 400 microns in a single pass would be to turn it. I typical ground finish would be closer to 0.4 Ra, but with 400 microns of stock to remove, would take multiple passes. Surface finishes of 2.0 Ra are easily attainable with turning. A more important question is "What is your tolerance of size?". A grinding process will probably allow a much tighter tolerance that turning.

 

[tripleZ]

We had a differential collar that required a 0.5 Ra finish on a face (not the OD). Stock removal was roughly the same amount as you dealt with. Typically, we could hit this finish using a two step process, removing the first 0.2mm with a rougher tool and the remaining stock with a wiper insert. The wiper geometry gave a far superior finish to a standard CBN tool. Now, to get it statistically capable we had to add a diamond burnisher for a 3rd pass as the wear rates on the inserts were higher than we would have liked with the material. My guess would be that you'll be cutting two passes minimum. As to speeds and feeds you may have to experiment based on inserts and stock removal rates.